1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, a method of producing an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus that include an electrophotographic photosensitive member.
2. Description of the Related Art
Electrophotographic photosensitive members that contain organic photoconductive substances are mainly used as electrophotographic photosensitive members installed in process cartridges and electrophotographic apparatuses. Such electrophotographic photosensitive members have good film-forming properties and can be produced by coating, and thus are advantageous in that productivity of the electrophotographic photosensitive members is high.
An electrophotographic photosensitive member typically includes a support and a photosensitive layer formed on the support. Furthermore, an undercoat layer is often provided between the support and the photosensitive layer in order to suppress charge injection from the support side to the photosensitive layer side and to suppress occurrence of image defects such as black dots.
In recent years, charge generating substances having higher sensitivity have been used in electrophotographic photosensitive members.
However, as the sensitivity of the charge generating substances increases and the amount of charges generated increases, charges tend to remain in the photosensitive layers, resulting in a problem called ghosting. Specifically, a phenomenon so-called positive ghosting in which only the density of a portion irradiated with light during the previous rotation is increased in an output image tends to occur. To address this problem, techniques for suppressing a change in the potential are disclosed in which an undercoat layer having an electron transporting capability (hereinafter, also referred to as “electron transporting layer”) is provided by incorporating an electron transporting compound in the undercoat layer.
Japanese Patent Laid-Open Nos. 2001-83726 and 2003-345044 describe techniques for suppressing the positive ghosting by incorporating an electron transporting compound such as an imide compound in an undercoat layer.
Japanese Patent Laid-Open No. 9-197701 describes a technique for suppressing the positive ghosting by incorporating an electron transporting compound and an organometallic compound having a metal element such as Zr or Ti in an undercoat layer.
In recent years, requirements for the quality of electrophotographic images have become higher and the permissible range for the positive ghosting has also become narrower. As a result of intensive studies conducted by the inventors of the present invention, it was found that the techniques disclosed in Japanese Patent Laid-Open Nos. 2001-83726, 2003-345044, and 9-197701 may not sufficiently suppress initial positive ghosting and have room for further improvements with regard to the suppression of initial positive ghosting.